1. Field of the Invention
The present invention relates to a terminal having Universal Serial Bus (USB) interface connecting function. More particularly, the present invention relates to a method and apparatus for controlling a system in dual power feeding mode of the terminal electrical power of which is fed from an electronic device to the terminal through the USB.
2. Description of the Related Art
Recently, as services using a public wireless Local Area Network (LAN) have increased in both availability and popularity, a high speed wireless Internet connection is formed typically using an electronic device such as a Personal Computer (PC), a laptop computer, a netbook computer, mobile terminal, etc. Such an Internet connection service through the public wireless LAN is now able to provide almost the same quality of service as in a wired environment. However, the Internet connection service has variously different degrees of coverage according to the particular network, inferior mobility, and is limited in being able to provide a service with high reliability and without deficiency. In order to overcome some of the shortcomings, there has been developed a portable terminal that is connected to Internet by accessing dual networks. Therefore, a user may use Internet services more conveniently through two different networks.
In order to feed sufficient electric power from an electronic device to a terminal having a USB function, a system has been constructed to utilize a USB cable or a battery provided in the terminal. In this case, the terminal may be a dongle type and is fed with the electric power from the electronic device by mounting an additional battery in the terminal or inserting cables into two USB ports of the electronic device respectively.
However, in order to feed a large amount of electric power from the electronic device to the battery of the terminal, the battery must have a large size relative to the terminal to have sufficient capacity to power prolonged operations. Due to this shortcoming, the terminal becomes larger in size than desired by consumer demand, poor in design, and relatively expensive as a price of the battery increases.
Moreover, in a case of charging a battery of the terminal using the electronic device, a temporary current shortage may occur in the electronic device due to the battery being charged.
In addition, when the terminal receives the electric power from the electronic device using a USB cable without providing a current limiting circuit, electric current fed from the electronic device cannot be limited, so that the operation of the electronic device may be limited in function because of the amount of current fed from the electronic device to other devices.